

A245044


Semiprimes with digits in descending order that differ exactly by 2.


0




OFFSET

1,1


LINKS



EXAMPLE

7531 is in the sequence because it is semiprime 7531 = 17*443 and 75 = 53 = 31 = 2.
97531 is in the sequence because it is semiprime 97531 = 7*13933 and 97 = 75 = 53 = 31 = 2.


MATHEMATICA

Sort[Flatten[Table[Select[FromDigits/@Partition[Range[9, 0, 2], n, 1], PrimeOmega[#]==2 &], {n, 1000}]]]


PROG

(PARI) for(d=1, 5, for(s=1, 112*d, t=sum(i=1, d, (s2+2*i)*10^i)/10; if(bigomega(t)==2, print1(t", ")))) \\ Charles R Greathouse IV, Jul 16 2014


CROSSREFS



KEYWORD

nonn,base,easy,fini,full


AUTHOR



EXTENSIONS



STATUS

approved



